The present invention relates to a suspension for disk drive incorporated in an information processing apparatus such as a personal computer.
A hard disk drive (HDD) for recording on or retrieving information from a rotating magnetic disk or magneto-optical disk includes a carriage that can turn around a shaft. The carriage is turned around the shaft by means of a positioning motor.
As described in U.S. Pat. No. 4,167,765, for example, the carriage is provided with an arm (actuator arm), a suspension on the distal end portion of the arm, a head portion including a slider attached to the suspension, etc. When the slider is slightly lifted from the disk surface as the disk rotates at high speed, an air bearing is formed between the disk and the slider.
The suspension comprises a load beam formed of a precise thin plate spring, a flexure formed of a very thin plate spring that is fixed to the distal end portion of the load beam by laser welding or the like, and a base plate fixed to the proximal portion of the beam by laser welding or the like. The base plate is fixed to a suspension mounting surface of the arm.
As the density of the information to be recorded on the disk and the operating speed of the disk drive of this type become higher, the seek time for the information is expected to be shortened. In order to shorten the seek time, the operation of a moving element (e.g., the aforesaid suspension) of the disk drive should be speeded up by reducing the weight of the moving element.
The suspension, such as a conventional suspension 1 shown in FIG. 12, comprises a load beam 2 and a base plate 3. A boss portion 4 is formed on the base plate 3. The base plate 3 is put on a proximal portion 2a of the load beam 2 and fixed to the proximal portion 2a by laser welding or the like. The load beam 2 includes a main portion 2b and a flat flexible portion 2c. The main portion 2b is enhanced in bending stiffness by means of reinforcing portions, such as bent edges 5 or ribs, formed thereon. When bending load acts on the load beam 2, therefore, the flexible portion 2c bends in a region near a front edge 3a of the base plate 3 that mainly serves as a supporting end for the load. Thus, the front edge 3a of the base plate 3 of the conventional suspension 1 is expected to extend at right angles to an axis C of the load beam 2. Accordingly, the base plate 3 used is substantially square.
Since area of the square base plate 3 is inevitably large, however, its weight can be reduced only limitedly. Since the front edge 3a of the base plate 3 serves as the load supporting end, moreover, the plate 3 must be accurately positioned with respect to its rotating direction (indicated by arrow R in FIG. 12) so that the front edge 3a extends at right angles to the axis C of the load beam 2. If the base plate is dislocated in the rotating direction R, as indicated by two-dot chain line F in FIG. 12, its front edge 3a skews at an angle to the axis C of the load beam 2, so that the spring properties of the flexible portion 2c change.
In order to locate the head portion on the suspension with high accuracy, the position of the base plate 3 on the load beam 2 must be accurately regulated with respect to the x- and y-axis directions shown in FIG. 12. For these reasons, the positioning operation for the fixation of the base plate 3 to the load beam 2 requires special consideration.
Conventionally, in fixing the suspension to the actuator arm, a swaging process is carried out such that the boss portion 4 is spread after it is inserted into a hole in the arm. If the base plate 3 of the conventional suspension 1 is deformed during this swaging process, the flexible portion 2c near the front edge 3a is easily influenced by the deformation. If the flexible portion 2c is influenced by the deformation, its spring properties change, so that the flying height of the head portion (slider) varies, and the resonance characteristic lowers.
Accordingly, an object of the present invention is to provide a suspension capable of reduction in weight and of preventing a load beam from being influenced by the deformation of a base plate. Another object of the invention is to provide a suspension in which a load beam and a base plate can be easily positioned with respect to each other.
In order to achieve the above objects, a load beam of a suspension according to the present invention comprises a beam body fixedly fitted with a flexure for supporting a head portion, a proximal portion fixedly fitted with a base plate, and a hinge portion situated between the beam body and the proximal portion and having bending stiffness lower than that of the beam body and the proximal portion, the base plate having a circular outer peripheral portion. When bending load acts on the load beam, the hinge portion bends, whereupon predetermined spring properties can be enjoyed. According to the present invention, the weight of the suspension can be reduced by making the round base plate lighter in weight. Thus, the weight of a moving element of a disk drive can be reduced to cope with higher-speed operation of the disk drive. Since the round base plate has no directivity with respect to its rotating direction, it can be easily positioned relatively to the load beam. If the base plate is deformed as the suspension is fixed to the actuator arm, moreover, the load beam cannot be easily influenced by the deformation.
The base plate includes, for example, a ring-shaped flange portion and a boss portion in the form of a short cylinder rising in the thickness direction of the base plate from the inner peripheral edge of the flange portion. The base plate can be positioned with respect to the load beam by putting the flange portion on the proximal portion of the load beam or by fitting the base plate into a circular hole in the proximal portion. According to the present invention, the base plate can be positioned more easily and accurately with respect to the load beam. The weight of the suspension can be further reduced by making the flange portion thinner than the proximal portion. Besides, the proximal portion of the load beam, which is higher in stiffness and accuracy than the base plate, can be put directly on a suspension mounting surface of the actuator arm.
In the load beam of the present invention, the beam body and the proximal portion may be separate components connected to each other by means of the hinge portion formed of a spring member. According to the present invention, the respective materials and thicknesses of the various parts including the beam body, proximal portion, and hinge portion can be optimized depending on their required properties.
Further, the beam body, the proximal portion, and the hinge portion, thinner than the beam body and the proximal portion, may be integrally formed of a common material. In this case, the hinge portion can be formed by reducing the thickness of a part of the material by partial etching or the like. According to the present invention, the beam body, proximal portion, and hinge portion are integral with each other, so that the number of components that constitute the load beam can be reduced, and the beam construction can be simplified.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.